When percutaneously treating a stenosed site which can cause, for example, myocardial infarction that occurs in a biological lumen such as a blood vessel, a vessel or the like, a diagnostic catheter can be used which acquires an image of a biological lumen using an inspection wave such as an ultrasound or light, in order to observe the properties of the stenosed site or the state of the stenosed site after treatment.
In intravascular ultrasound (IVUS) diagnosis, an imaging core which has an ultrasound transducer is rotatably provided at a distal end of an insertion portion and is inserted into a lumen in a living body, and then, performs scanning (radial scanning) while rotating through a drive shaft or the like which extends from a driving unit on a hand side.
In addition, in optical frequency domain imaging (OFDI) using wavelength sweep, radial scanning can be performed in a blood vessel by inserting an optical probe unit, into which an imaging core is interpolated to which an optical lens and an optical mirror (transmitting and receiving unit) is attached at a distal end of an optical fiber, into the blood vessel; emitting measurement light into the blood vessel from the transmitting and receiving unit at the distal end while rotating the imaging core; and receiving reflected light from a biological tissue. Moreover, a tomographic image of the blood vessel can be drawn based on interference light generated by allowing the received reflected light to interfere with reference light.
In the OFDI, an image with a relatively high resolution with respect to the lumen surface of a blood vessel can be obtained. However, only an image up to a tissue which is comparatively shallower from the lumen surface of a blood vessel is obtained. In contrast, in the case of the IVUS, an image of a vascular tissue which is deeper than that in the OFDI can be obtained, while the resolution of an obtained image is lower than that of the OFDI. In recent years, an imaging apparatus for diagnosis has been proposed which has an imaging core equipped with a dual sensor in which the function of the IVUS and the function of the OFDI are combined (refer to JP-A-11-56752).
With such an apparatus, a medical practitioner can evaluate an identical observation site using images including both the IVUS images and the OFDI images. For both of the IVUS and OFDI images, a plurality of tomographic images are acquired while performing a pull-back operation (operation of moving the imaging core to the hand side). Low speed pull-back (for example, 0.5 mm/sec) and high speed pull-back (for example, 20 mm/sec) are used together by switching the movement speed (pull-back speed) of the imaging core. In general, the quality of the image acquired through high speed pull-back is more deteriorated than that of the image acquired through low speed pull-back. For this reason, if possible, it is preferable to acquire an image through low speed pull-back. However, in the case of the low speed pull-back, it may be difficult to acquire an image through OFDI since it is impossible to continue flushing. In contrast, an image through IVUS can be acquired in all of the cases of the low speed pull-back and the high speed pull-back.
It may be necessary to evaluate an identical observation site using IVUS images which are acquired through low speed pull-back and OFDI images which are acquired through high speed pull-back.
However, the IVUS and the OFDI are modalities (imaging devices) different from each other. Therefore, it may be difficult to align IVUS images which are acquired through low speed pull-back and OFDI images which are acquired through high speed pull-back with respect to an identical observation site. In this manner, it can be difficult to align the images using different modalities. The present disclosures provide a technique that facilitates the alignment between images using different modalities.